This research project is intended to gain understanding of the interactions between the cellular elements of the nervous system and the modification of these interactions by previous activity. Experiments are proposed utilizing electrophysiological, fluorometric and morphological techniques to study the functional interdependence of neurons and glia. Following degeneration of the axons the properties of the isolated glial cells will be studied. Glial cell turnover will be studied by autoradiography in the presence and absence of nerve axons and during axonal degeneration. Additional emphasis is on processes enabling glial cells to control their ionic environment as well as the external environment of neurons. Further studies on the metabolic responses of glia to alterations in the ionic environment and on the membrane characteristics of glia are also proposed. A second line of investigation utilizes the buccal ganglion and buccal mass of Aplysia to continue studying the physiological, pharmacological and morphological basis of excitatory and inhibitory interactions in the control of activity of molluscan muscle.